Ok I understand tha at WOT the O2's are not used and the engine enters enrichment mode. The BLM's will be 128 on both sides.

When I dynoed last my engine appeared to be very rich at WOT. I contacted Ion and he sent me a leaner tune. I have not been back to the dyno to see if it has leaned out.

1. I know you need to have a wide band O2 in order to see accurate WOT A/F mixture, but what is the next best way to check this? I have a laptop, Freescan, Datamaster.

2. How are adjustments made to the A/F mixture with respect to WOT conditions only?

3. Can the PCM make adjustments to the A/F mixture at WOT on the fly.

Thanks

 

Im pretty sure the computer does not make a/f changed at WOT, it just runs of preset data, and values it collects while you are driving normal. The compute does not monitor emission at all at wot.

 

changes are made using the wot vs. rpm and vs. coolant temp tables in the computer.

You can monitor it in a general sense by looking at the O2 sensor values. Usually you want low 900s at wot.

 

I am currently getting 860-880mv.

I assume that Ion can provide a tune that will bump this up to the low 900's. I want the most power possible but still be on the safe side.

Is this correct? Would this make it more rich or more lean?

 

Reognizing the limitations of the stock O2 sensors, increasing the WOT mV's from 880 to 900+ would indicate that you have succeded in richenign the mixture. It would not tell you whether that is the correct A/F ratio for peak power and torque. That's what you get from a real dyno tune.... varying A/F ratio and ignition advance over wide ranges to find the combination of timing and A/F ratio that give you max power and torque. There is no "fixed" answer..... each particular combo of heads, cam, quench, etc is likely to give you a different optimum point.

860-880 would ROUGHLY indicate that you are running near the level that many people find produces the best results, at 13.0:1 +/- 0.2. If you feel that's too rich (why do you feel its "very rich"?) bumping up to 900mV would only make it worse. But that's a ROUGH indication... you can't tune accurately with narrow-band O2 sensors.

Also, it is no a "given" that the BLM's will stay at 128 at WOT (actually called PE or Power Enrichment mode). If the closed loop BLM's are "cutting" fuel, the PCM will use Cell 15 or Cell 18 at WOT and lock the BLM's at 128. However, if your closed loop BLM's were "adding" fuel (above 128) the PCM will use the BLM's in Cell 15 at WOT, not 128.

 

So a higher value is more to the richer side and a lower value is more to the leaner side.

The reason I claim mine to be rich at WOT can be seen in my dyno graph, the A/F drops to 12:1 or so:

I definitely do not want to further richen the mixture.

I understand that there are no certainty's without going to the dyno, I am still learning what all this stuff means. Thanks for the replies.

I am considering a dyno tune but they want $400 to do it, that to me sounds pretty expensive for the net gains I will see. I am convinced that things are reall close to where they want to be.